Cummins exhaust brake stopped working

[KRStone]

My dad's '06 3500 came with the factory or dealer (not sure which) cummins exhaust brake / trans lockup switch on the gear selector.



His engine brake stopped working. Just had it into a dealer for an A/C recharge. Now it stopped working. I checked the rubber air lines from the E. B. to a solenoid behind the battery, then from the solenoid up around the firewall cowl to a vacuum fitting in the wiring harness. It all looked good. What else should I check.



If there is a solenoid, there must be a fuse, right?



I know the aftermarket pacbrake on my '96, but this setup on my dad's '06 is new to me.



Thank you,

KRS

 

[ScottLewis]

IMO, the most likely culprit is the vacuum pump, probably the diaphragm. Since the pump operates full time, vacuum can be checked by removing a hose. There's quite a bit of info on the forum about them and potential cures. I wound up swapping mine out for a PAC Brake which activates by air pressure. There are cheaper solutions too, such as replacing the pump/diaphragm or adding an electric vacuum pump.
The switch on the gear selector of the '06 turns the brake on and off and the ECM does everything else like locking and unlocking the TC, actuating the brake, etc.

 

[jhenderson]

If the pump is making vac, check to see if the relay is activating. Truck off, key on, you should hear the relay click when the switch is operated. Does the light on the switch come on? If not run the harness for a fuse, and check the 2 connections at the computer on the side of the motor. Then check for power at the switch. I just had a switch go bad last week.

 

[KRStone]

Just checked fuse behind driver battery, it was good.

Pulled hoses off both sides of solenoid, started truck, held hoses together (bypassing solenoid) and EB worked! So, it's not the vacuum pump.

Tonight I will check relay and solenoid.

 

[KRStone]

Hmmmm, had A/C recharged just before the EB quit working. Found EB relay and it's blocking a path to the A/C back by the firewall. I wiggled it all, disconnected relay connected and put it back together, and the EB works.

I can surmise that the tech who did the a/c jammed his arm in there bending those wires, and now i have a wire with broken copper wires inside..... just not sure which one

 

[KRStone]

The e.b. relay was mounted to the firewall with a screw. The relay hid a ring terminal also on the screw. The ring terminal wasnt grounding properly.
Moved the ring terminal to the neg batt cable, used the screw to hold the relay.

Works great now. Took me months to fjnd the time to work on it.